BOSTON -- Infants who pack on the pounds in their first six months may be at an increased risk of childhood obesity, researchers here said.

Action Points

Explain to interested patients that rapid increases in weight for length in the first six months of life were associated with a sharply increased risk of obesity by age 3.

Note that the findings suggest that early interventions to prevent rapid increase in weight status in the first months of life may help reduce children's risk of obesity later in childhood.

BOSTON, March 30 -- Infants who pack on the pounds in their first six months may be at an increased risk of childhood obesity, researchers here said.

Rapid increases in weight for length in the first six months of life were associated with a seven-fold increased risk of obesity by age 3, Elsie Taveras, M.D., M.P.H., of Harvard Medical School, and colleagues reported in the April issue of Pediatrics.

"Mounting evidence suggests that infancy may be a critical period during which to prevent childhood obesity and its related consequences," Dr. Taveras said.

During the past 30 years, the prevalence of overweight among children in the U.S. has increased dramatically, the researchers said. Previous studies have correlated birth weight and obesity, but some of those were limited because they didn't add height or length to their equations.

Measures of size that include length in addition to weight reflect adiposity better than does weight alone, the researchers said, so they examined "weight-for-length," which takes both factors into account.

So to examine the extent to which weight-for-length at birth and at six months was associated with obesity at age 3, the researchers looked at a subset of 559 children in the larger Project Viva, an ongoing prospective cohort study of pregnant women and their children.

They measured length and weight at birth, six months, and then again at 3 years.

At 3 years, 9% of children were obese.

The researchers found that rapid increases in weight-for-length in the first six months of life were associated with a sharply increased risk of obesity at age 3.

Each increment in weight-for-length z-scores at six months was associated with higher odds of obesity at age 3 (OR 6.84, 95% CI 3.84 to 12.19).

Each increment was also associated with higher BMI z-scores, as well as higher sums of subscapular and triceps skinfold thicknesses at that age.

The researchers said that predicted obesity prevalence among children in the highest quartiles of weight-for-length z-scores at birth and six months was 40%, compared with 1% among children in the lowest quartiles.

Also, weight-for-length measurements at six months were more strongly related to risk of obesity than weight-for-length measurements at birth.

"Early interventions to prevent rapid increase in weight status in the first months of life may help reduce children's risk of obesity later in childhood," the researchers said.

The study may be limited by a lack of generalizability. Also, the researchers could not assess whether breastfeeding mediated the relationship between changes in weight-for-length in infancy and later obesity.

"Future studies should examine whether the mode of infant feeding, the quality of the infant diet after weaning, and overfeeding because of lack of parental responsiveness to infants' satiety cues might explain the association of infant weight gain with later obesity," they said.

Finally, they noted, "Obesity at this age does not predict adult consequences as well as obesity later in childhood but can presage serious adverse health consequences in childhood itself."

The researchers concluded that the increasing prevalence of childhood obesity should spark urgent prevention efforts.

The study was supported by a grant from the NIH and by the Physician Faculty Scholars Program of the Robert Wood Johnson Foundation.

The researchers reported no conflicts of interest.

Reviewed by Zalman S. Agus, MD Emeritus Professor University of Pennsylvania School of Medicine

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